1. Field of the Invention
The present invention relates to the fields of carbon nanotube technology and molecular biology. In particular, the invention relates to methods and composition for producing large numbers of distinguishable labels comprising carbon nanotubes. More particularly, the invention relates to compositions, apparatus and methods of use of carbon nanotube labels for DNA (deoxyribonucleic acid) sequencing and other applications.
2. Background
Carbon nanotubes may be thought of as sheets of graphite that have been rolled up into cylindrical tubes. The basic repeating unit of the graphite sheet consists of hexagonal rings of carbon atoms, with a carbon-carbon bond length of about 1.42 xc3x85. Depending on how they are made, the tubes may multiple walled or single walled. A typical single walled carbon nanotube (SWNT) has a diameter of about 1.2 to 1.4 nm.
The structural characteristics of nanotubes provide them with unique physical properties. Nanotubes may have up to 100 times the mechanical strength of steel and can be up to 2 mm in length. They exhibit the electrical characteristics of either metals or semiconductors, depending on the degree of chirality or twist of the nanotube. Different chiral forms of nanotubes are known as armchair, zigzag and chiral nanotubes. Carbon nanotubes have been used as electrical conductors and as electron field emitters. The electronic properties of carbon nanotubes are determined in part by the diameter and length of the tube.
Many existing methods of use in molecular biology would benefit from the availability of a highly diverse set of tag molecules that could be used as molecular labels to detect binding of specific analytes to various ligands. For example, the speed and efficiency of nucleic acid sequencing would be greatly enhanced by the availability of unique labels capable of identifying all possible nucleic acid sequences for oligonucleotides of five, six, seven, eight or even more nucleotide residues in length. At present, no such set of distinguishable labels with the required degree of diversity exists.